What Is a Sodium Blood Test?

A sodium blood test is a routine test to help your doctor learn more about your health. It is also called a serum sodium test.

Why Is the Sodium Blood Test Done?

Sodium is a mineral essential to your body. It is also referred to as Na+ or natrium. Sodium is particularly important for nerve and muscle function.

Your body keeps sodium in balance through a variety of mechanisms. Sodium gets into your blood through food and drinks. It leaves the blood through urine, stool, and sweat.

Having the right amount of sodium is important for your health. Too much sodium can raise your blood pressure. A lack of sodium can cause symptoms such as:

nausea

vomiting

exhaustion

dizziness

The sodium blood test is often part of a basic metabolic panel. A panel is a group of related tests. The basic metabolic panel includes tests for:

calcium

carbon dioxide (CO2)

chloride

creatinine

glucose

potassium

sodium

blood urea nitrogen (BUN)

Blood sodium can also be part of an electrolyte panel. Electrolytes are substances that carry an electrical charge. Potassium and chloride are other electrolytes.

This test may be ordered if you have:

eaten large amounts of salt

not eaten enough or had enough water (dehydration)

had a serious illness, recent injury, or gone through surgery

received intravenous (IV) fluids

You may also receive this test to monitor medications that affect your sodium levels. These include diuretics and certain hormones.

How Is the Sodium Blood Test Done?

This test is performed on a blood sample. The sample will be obtained by venipuncture. A technician will insert a small needle into a vein on your arm or hand. This will be used to fill a test tube with blood.

How Do I Prepare for the Sodium Blood Test?

You do not need to prepare for this test. Eat normally and drink a normal amount of water before going to the testing site.

You may have to stop taking certain medications before this test. However, drugs should only be stopped on a doctor’s instructions.

What Are the Risks of the Sodium Blood Test?

When the blood is collected, you may feel some moderate pain. There may also be a mild pinching sensation. Any discomfort should only last a short time. After the needle is taken out, you may feel a throbbing sensation. You will be instructed to apply pressure to the puncture. A bandage will be applied.

There are few risks to taking a blood sample. Rare problems include:

lightheadedness or fainting

hematoma—a bruise under the skin

infection

excessive bleeding

If you bleed for a long period after your test, it may indicate a more serious bleeding condition. Excessive bleeding should be reported to your doctor

Understanding the Results of a Sodium Blood Test

Normal Results

Normal results for this test are 135 to 145 mEq/L(milliequivalents per liter). However, different laboratories use different values for “normal.” Some labs go as high as 153 mEq/L.